1. Field
The present disclosure relates to a system and a method for gray balance calibration in an image printing system.
2. Description of Related Art
Color image printing systems typically employ a plurality of inks of different primary colors to generate a spectrum of colors. For example, some color image printing systems use four ink colors: cyan (C), magenta (M), yellow (Y) and black (K). Color images are formed on a receiving substrate or medium by placing combinations of zero or more dots of C, M, Y or K ink at each pixel location. Cyan, magenta and yellow are typically employed since a wide range of colors can be produced by different combinations of these inks
Ideally, equal amounts of C, M and Y inks should result in a gray color. However, due to a variety of factors, equal amounts of C, M and Y commonly do not produce gray colors, and image printing systems are commonly configured to perform gray balancing. For example, gray balancing can involve adjusting the amounts of C, M, and/or Y so that when the input color data contains equal amounts of CMY, the printed output is gray or substantially corresponds to a black output of the same density.
In image printing systems, all four colors of the image printing system are contained in each print head and are calibrated during print head manufacturing as a single unit. The relationship of intensity and/or drop mass of the individual colors to the other colors within the print head can be controlled during the manufacturing calibration process. This manufacturing process provides adequate control of the secondary and composite gray hue in the some image printing systems with a single print head platform.
In other image printing systems, where four print heads are assembled and are calibrated into one unit. A reference print head is first selected and the overall intensity and color balance in the other three print heads are normalized with respect to the reference print head in order to achieve the customer requirements for intensity and hue.
In image printing systems with a multi-print head platform, where four mono-color print heads are combined to produce a four-color image printing device, control of the head to head intensity is required to control the resulting hue in the secondary and composite gray colors. Setting drop mass on each of the four print heads is often too expensive and may not possible if the print head needs to be replaced. Therefore, a method to establish the intensity relationship among the four print heads is desired.